1. Field
The following description relates to a technology for expanding the ISO sensitivity of a camera.
2. Description of the Related Art
International Standard Organization (ISO) sensitivity represents a rated degree to which a camera responds to light. Digital cameras are able to adjust the ISO sensitivity depending on a user's setting and taking into consideration the surrounding environments. For example, in a low light photographing condition, a user may increase the ISO sensitivity value to achieve a sufficient shutter speed, thus avoiding issues traditionally associated with low light conditions such as camera shake. That is, an increase in ISO sensitivity may be useful to avoid using a long exposure time or slow shutter speed in low light photographing conditions.
Meanwhile, a digital camera may be provided with an image sensor which responds to light to output an electric signal. The image sensor discharges electric current in response to light but may generate a dark current due to sources other than light. Such a dark current results in noise in images.
One method of increasing the ISO sensitivity of digital camera may be achieved by amplifying output current of an image sensor. However, this also may cause dark current to be amplified, thereby amplifying noise in images. In addition, image sensors for use in digital cameras or camera phones have been developed to be more compact and to have a higher sensitivity. This may also cause a high level of noise.
The noise due to the increase in the ISO sensitivity may be removed through various noise removing methods. However, the increase in the ISO sensitivity also causes a degradation of image quality.